Collagen is a protein which is the main component of extracellular matrix filling the spaces between cells or groups of cells in living tissues and is said to sometimes comprise nearly 30% of the total protein in the body of mammals (see non-patent document No. 1).
Collagen forms a fibrous structure or a membrane structure and its primary function is to maintain, support, bind and reinforce the tissue structure. Collagen exists in abundance in skin, bones, tendons, ligaments, cornea, blood vessels, etc. Decrease and denaturation of tissue collagen is considered to be a major factor for wrinkles, sagging skin, osteoporosis and the like which are induced by aging of these tissues. Actually, there are reports that tissue collagen remarkably decreases by long time exposure to sunlight (see non-patent document No. 2) and that lowering of metabolism of living components accompanying aging is triggered by the lowering of metabolism of collagen (see non-patent document No. 3).
Substances known to promote the synthesis of collagen include TGF β-1, which is a growth factor (see non-patent document No. 4), a plant extract (see patent-document No. 1), hydrolyzed collagen (see patent document Nos. 2 to 5) and an amino acid composition (see patent document No. 6). More specifically, the tripeptide Gly-Pro-Hyp is known as a sequence characteristic of hydrolyzed collagen showing the activity to promote the synthesis of collagen when orally ingested. However, it is also known that an amino acid composition whose constitutive ratio of constituent amino acids such as Gly, Pro and Hyp was made equal to that of collagen does not show the activity to promote the synthesis of collagen (see patent document No. 4).
On the other hand, an N-acyl derivative of hydroxyproline is known to have the activity to promote the synthesis of collagen when orally ingested (see non-patent document No. 4), and an external medicine containing an N-acetyl derivative of hydroxyproline is used as a wound-healing agent in Europe. It is also known that hydroxyproline and an N-acyl derivative of hydroxyproline have collagen synthesis promoting effect on cultured human fibroblasts, and when externally applied, they have the activity to prevent or decrease the formation of wrinkles (patent document No. 7). However, unknown are the activity to promote the synthesis of collagen, the activity to promote the healing of skin wounds and the activity to prevent or improve skin wrinkles or sagging of orally ingested hydroxyproline.    Patent document No. 1:    Japanese Published Unexamined Patent Application No. 35527/04    Patent document No. 2:    Japanese Published Unexamined Patent Application No. 278012/95    Patent document No. 3:    Japanese Published Unexamined Patent Application No. 201649/00    Patent document No. 4:    Japanese Published Unexamined Patent Application No. 131084/01    Patent document No. 5:    Japanese Published Unexamined Patent Application No. 137807/03    Patent document No. 6:    Japanese Published Unexamined Patent Application No. 289928/05    Patent document No. 7:    WO2000/051561 pamphlet    Non-patent document No. 1:    Seikagaku Jiten (Biochemical Dictionary), First Edition, Tokyo Kagaku Dojin, p. 480 (1984)    Non-patent document No. 2:    Karei to Hifu (Aging and Skin), Seishi Shoin, p. 35 (1986)    Non-patent document No. 3:    Mechanism and Control of Aging, IPC, p. 151 (1993)    Non-patent document No. 4:    Experimental & Molecular Pathology, Vol. 28, No. 1, p. 58-64 (1978)